Members of New York’s nearly permanent, always vibrant, underground free music scene, the improvisers here not only play in different configurations, but work avidly to promote the music. Tenor saxophonist Ras Moshe and alto saxophonist Blaise Siwula each organize regular improv sessions, while all the players welcome free-form gigs here or overseas, whether it’s with major stylists such as saxophonist Joe McPhee or interesting tyros.

The spectacular result of years of selfless music-making is on this CD. Recorded in guitarist Dom Minasi’s flat, the players take post-Ascension advances as a benchmark and cram as many bent notes, extended timbres and alternate harmonies as necessary into these improvisations. But technical extensions aren’t used as solipsistic showiness but as methods to interact with the ensemble itself or in duo or trio interludes.

Different players step forward at different times. Bassist Albey Balgochian’s scrubbing and splintering stops are showcased on “Hey Cowboy” for instance; others have more space. Beating out rhythmic hooks throughout, drummer Jay Rosen lets loose with focused rim shots, cowbell slaps, cymbal pops plus rebounds on the same track, while Minasi uses slurred fingering to first goose the tempo, then after staccato group variations, prods the others to harmonize.

Staccato and fortissimo exchanges interest both horn players. Moshe for example, studs “Atmospheric Meeting” with irregular diaphragm vibratos, reed stutters and disassociated honks, contrasting with Siwula’s lip-trembling contralto clusters. Nearly continuous in their blowing, the saxes are backed by Rosen’s cowbell whacks and the guitarist’s intricate fills. Meanwhile, on the title track, the tenor saxophonist’s tone shards harden into a “Taps”-like theme, aptly accompanied by the drummer’s martial rat-tat-tats. That intermezzo is followed by layered reed vamps, bass wood creaks and guitar arpeggios, that produce a piece as linear as it is mercurial.

This CD is a first-class essay in the art improvisation that could only be fashioned by musicians with years of similar experiences.

Tracks: Atmospheric Meeting; Stop Ringing Those Dam Bells; The Bird, The Girl and The Donkey; Hey Cowboy; Sonia’s Back, No Really, Her Back